Abstract

'In a colony of captive koalas, all aggressive behaviour was a variation on the single motor pattern of throwing a foreleg around an opponent and biting. Squabbles (the most common aggressive behaviour) were brief, low level interactions usually arising from the efforts of one koala to climb past or over another. Minor fghts involved only single bites and the combatants stayed in the same place; major ,fights involved multiple bites and changes of position. Dependent young were seldom involved in aggression. Between males. minor fights were essentially intensified squabbles, but major fights involved wrestling and chasing; they were more likely between males unfamiliar with each other, or those already aroused by, e.g., other aggressive interactions. Females became aggressive especially during pregnancy and at the end of lactation. At such times they stood their ground and vocalized at other koalas, especially males, but attacked only if the opponent came within reach. Although the opponent usually withdrew. sometimes a male seemed provoked to attack. Males sometimes attacked females without obvious provocation. Aggression was slightly more common in than outside the breeding season. Competition for females or food, dominance hierarchies, appeasement, and the defence of young were not seen.